Precision lapping machine



March 11, 1958 c. ROSER PRECISION LAPPING MACHINE mm 1m. 31. 1954 6 Sheets-Sheet 1 m m E C. ROSER PRECISION LAPPING MACHINE Mgrch "11, 1,958

6 Sheets-Sheet 2 mm Dec, 51, 1954 INVENTOR.

' s/fa Pose?" BY C. ROSER PRECISION LAPPING MACHINE Marchll, 1958 6 Sheets-Sheet 3 Filed Dec. 31;, 1954 INVENTOR.

March 11, 1958' c. ROSER 2,826,010 I PRECISION LAPPING MACHINE Filed Dec. 31, 1954 e She'Ls-Sheet 4 C. ROSER PRECISION LAPPING MACHINE March IL 1958 Filed. Dec. 51, 1954 6 Sheets-Sheet 5 &

March H, 195% c. ROSER PRECISION LAPPING MACHINE 6 Sheets-Sheet 6 Filed Dec. :1, 1954 T R. w M m ME fl m@ L United States Patent 2,826,010 PRECISION LAPPING MACHINE Christian Roser, Villingen, Schwarzwald, Germany, assignor to John Haller, Northville, Mich. Application December 31, 1954, Serial No. 479,139 8 Claims. c1. 51-157 This invention relates to lapping and, in particular, to precision lapping machines.

One object 'ofthis invention is to provide a precision lapping machine for the accurate lapping of bores wherein the bore remains accurately straight from end to end and its diameter remains accurately constant up to the very end of the bore, without any appreciable flaring of the bore,'as has occurred in prior lapping machines and under prior lapping conditions.

Another object is to provide a lapping machine of the foregoing character wherein there is provided an automatically-expansible lapping tool which is automatically increased in diameter as the lapping proceeds, so that as the bore increasesin diameter as a result of the lapping operation, the lap also automatically increases in diameter.

Another object is to provide a precision lapping machinehaving a plurality of spindles or pairs of spindles, therotation of which can be started and stopped independently of one another, so that work may be inserted or removed from one spindle without disturbing other spindles, thereby economizing in time and labor and increasing the efficiency of the lapping machine.

Another object is to provide a precision lapping machine of the foregoing character wherein the lapping compound is fed automatically to the bore being lapped, so' as to supply fresh lapping compound as it is needed, without requiring the attention 'ofthe operator, thereby preventing the supplying of lapping compound at too rapid or too slow a rate of feed, as has occurred hitherto in prior lapping machines, and consequently avoiding the inaccuracy hitherto resulting from such improper feeding of lapping compound.

Another object is to provide a precision lapping mahine of the foregoing character which can be equipped with an external lapping unit which fits into the machine in place of the internalla'pping' unit, the externallapping unit being interchangeable with the internal lapping unit in a quick and easy manner.

Other objects and advantages of the invention will become apparent during the course of the following description of the accompanying drawings, wherein:

Figure 1 is a topjplan'view, partly in horizontal section, of a precision lapping'machine, according to one form of the invention;

"Figure 2 is a vertical longitudinal section along one of the lapping spindles, taken along the line 2-2 in Figure 1, showing the irregular motion mechanism for increasing the accuracy of lapping;

Figure 3\is a vertical cross-section through the precision lapping machine of Figures 1 and 2, taken along the line '3-3 in Figure 2;showing the mechanism drivingly interconnecting the'two sets of spindles;

Figure 4 'isan enlarged vertical cross-section through a pair of lapping tools and their adjacent mechanism, showing the automatic lap-expanding mechanism;

Figure 5 is an enlarged vertical cross-section taken along the line 5-5 in 'Figure 2, showing the automatic lapping compound feeding mechanism for each pair of lapping tools;

Figure 6 is an enlarged vertical section through the work holder and expansible lapping tool, taken along the line6-6 in Figure 1;

Figure 7 is a vertical cross-section taken along the line 2,826,010 Patented Mar. 11, 1958 ice 5 Figure 7 in side elevation;

Figure 9 is a vertical longitudinal section taken along the line 9-9 in Figure 4, showing further details of the automatic lapping tool expansion mechanism;

Figure 10 is an enlarged fragmentary vertical section taken along the line 10-10 in Figure 3, showing the parts of the stroke-adjusting mechanism in a long stroke position;

Figure 11 is a view similar to'Figure 10, but showing the parts of the stroke-adjusting mechanism in a short stroke position;

Figure 12 is a fragmentary view of one end of a pinion rod used for adjusting the stroke of the stroke-adjustment mechanism of Figures 10 and 11;

Figure 13 is a fragmentary vertical longitudinalsection taken along the line 13-13 in Figure 3,,showing the details of the power transmission gearing to the .workpiece rotating shaft;

Figure 14 is an enlarged vertical section, partly in side elevation, of the expansible lapping tool shown in the central portion of Figure 6;

Figure 15 is a cross-section taken along theiline 15-15 in Figure 14;

Figure 16 is an enlarged vertical section taken along the line 16-16 in Figure 1, showinglthe selective clutching mechanism for independently operating each pairof work holding spindles;

Figure 17 is a fragmentary side elevation, partly in vertical section, of theyright-hand side portion of Figure-2, showing the internallapping unit removed and replaced by an interchangeable external lapping unit;

Figure 18 is a verticalcross-section, partly in elevation, taken along the line 18-18 in Figure 17;

Figure 19 is an enlarged vertical cross-section, partly in elevation, taken along the line 19-19 in Figure 17;

Figure 20 is an enlarged vertical cross-section, looking in the opposite direction from Figure 19, and taken along the line 20-20 ,inFigure 17; and

Figure 21 is a vertical cross-section taken along the line 21-21 in Figure2, showing the forked crank and quadrant gear mechanism for. reciprocating the workpiece holder while it is being rotated.

General arrangement Referring ,to the drawings indetaiLFigures land 2 show a precision lapping machine, generally designated 30, according to one form of the invention as consisting of .two paired lapping assemblies, generally designated 32 and '34,.respectively, drivinglyinterconnected by aselective clutching device, generally designatedt36, whereby theIapping assemblies 32 and 34; may be operated independently of one another so that one assemblymay be halted for insertion or removal of workpieces or for other purposes while the other assembly is operating. The two lapping assemblies 32 and 34 are substantial duplicates of one another, hence their corresponding partsare designated with similar reference numerals and a single description will suflice for both assemblies 32 and 34. Each lapping assembly 32 and 34 of the machine shown in Figures 1 .to v16 inclusive istequipped with an internal lapping unit, generally designated 38, these being removable and replaceable with an external lapping unit generally designated 40, shown in Figures 17 to 20 inclusive.

The lapping machine 30;is provided \with a housing structure, generally designated 42, which also serves as a supporting frame for the various, mechanisms. ,The housing structure 42, for clearness of showing, is illustrated as being open in Figure 1, whereas in practice the l'fi it various mechanisms are protected by cover plates and shields in order to protect them from dust and other foreign matter as well as to prevent the escape, splashing or spattering of lubricant outside the machine. The

I housing structure 42 has a main portion 44 shown at the left-hand side of Figures 1 and 2, and a pair of extensions 46 for carrying the work holders and the internal or external lapping units 38 or respectively. The housing structure 42 is mounted upon the usual base plate (not shown) but located at the bottom of the structure shown in Figure 3 and having outer and inner spaced parallel Walls 48 and 50 respectively supported thereon .and rising therefrom. The four spaced vertical longitudinal walls 48 and 50 are interconnected by opposite practice, of course, certain portions of these walls are removable in order to obtain access to the various mechanisms.

Selective clutching device Journaled in a bearing boss 56 in the central portion of the end wall 52 of the housing structure 42 is a main drive shaft 58 (Figure 1) on the outer end of which a pulley 60 is pinned, splined or otherwise drivingly secured. In the machine as actually constructed, the pulley 60 is itself covered by a housing, and is driven by a belt from an electric motor (not shown) concealed in the lower part of the housing structure 42. Keyed or otherwise drivingly secured to the inner end of the main drive shaft 58 is a bevel pinion 62 which meshes with two bevel ring gears 64 on cup-shaped clutch housings 66 of two conventional multiple disc clutches, generally designated 68. The clutches 68 are similar to one another in construction and have hubs 70 mounted for opposite directions of rotation on a stationary shaft 72 (Figure 16). The stationary shaft 72 at its opposite ends is mounted in bores 74 in the inner housing walls 50 and is held in position by the bases 76 of angle brackets 78 secured to the walls 50 by bolts 80.

Drivingly and slidably secured as at 82 (Figure 16) to each clutch housing 66 are multiple outer clutch discs 84 which are interleaved with inner multiple clutch discs 86 drivingly and slidably secured as at 88 to the clutch hub 90 which is loosely rotatable on the stationary shaft 72. Fixedly mounted on the clutch hub 90 is a clutch disc abutment 92 against which the alternately arranged inner and outer clutch discs 86 and 84 are urged into frictional driving engagement with one another by an axially-slidable ring 94. The ring 94 is moved axially for this purpose by bellcrank levers 96 pivotally mounted on the pins 98 which in turn are mounted in the hub 90 ad extend across slots 100 receiving the bellcrank levers The opposite ends of the bellcrank levers 96 are engaged by an internal conical surface 102 on an axiallymovable grooved clutch-shifting ring 104 which is slidably mounted on the clutch hub 90 and is shifted to and fro by a conventional clutch-shifting yoke 106 secured to a vertical shaft 108 mounted in a bracket 110 secured to the inside of the end wall 52 of the housing structure 42. Each clutch-shifting yoke 106 carries a pair of diametrically-opposite pins or rollers 112 (Figure 3) which engage the grooved clutch-shifting ring 104 to shift it to and fro. Clutch-shifting is accomplished by turning each. vertical yoke shaft 108 by means of a handle 114 pinned or otherwise secured to its upper end above the top wall 115 of the housing structure 42 through which the clutchshifting shafts 108 pass (Figure 3). As a consequence, by shifting either of the handles 114 to and fro, the multiple disc clutches 68 are caused to engage or disengage so as to transmit rotary motion from the ring gears 64 to the clutch hubs 90 and thence to gears 116 integral. with or mounted on the clutch hubs 90.

Work-rotating and reciprocating mechanism The construction of the lapping assembly 32 is substantially identical with the lapping assembly 34, and both are similarly driven from their respective clutch output gears 116, hence a single description will be sufficient for both assemblies. Meshing with each of the clutch output gears 116 is a gear 118 keyed or otherwise secured to a horizontal shaft 120 which is journaled in a bearing boss 122 on each inner wall 50 of the housing structure 42 (Figures 2 and 3) and has a bevel pinion 124 keyed or otherwise secured to its opposite end. The bevel pinion 124 meshes with and drives a bevel gear 126, the hub of which carries a spur gear 128, both being loosely and rotatably mounted on a headed stationary stub shaft 130, the opposite end of which is seated in the upper end of the bracket 78. The spur gear 128 meshes with an idler pinion 132 (Figures 3 and 13) which is loosely and rotatably mounted upon a flanged bearing bushing 134 having a bearing bore 135 therein. The bushing 134 is seated in a bore 136 in a wall or web 138 extending between the outer and inner walls 48 and 50 of the housing structure 42 and secured therein by a nut 140 threaded on the opposite end of the bearing bushing 134 from the idler pinion 132.

The idler pinion 132 meshes with a pair of pinions 142 and 144 drivingly connected to parallel outer tubular shafts 146 and 148 (Figure 3) of similar construction and purpose but designated by different reference numerals because the outer tubular shaft 146 at its opposite end carried an additional pinion 150 not found on the outer tubular shaft 148 (Figures 1 and 2). The outer tubular shafts 146 and 148 are mounted for free rotation between the wall 138 and the end wall 54 of the housing structure 42 (Figure 2) and have bores 151 therethrough. Each of the outer tubular shafts 146 and 148 is keyed at 152 to an axially-slidable inner tubular shaft 154 which passes entirely through the bore 151 of its respective outer tubular shaft 146 or 148 and emerges at the opposite ends thereof, each inner tubular shaft 154 being considerably longer than its respective outer tubular shaft 146 or 148 and having a bore 155 therethrough. The rearward flanged end 156 of each inner tubular shaft 154 is rotatably mounted in a bearing bore 158 in a cross head 16%) (Figures 1 and 2) and held in position by a collar 161 pinned or otherwise secured to the shaft 154. The cross-head is reciprocated by a rack shaft 162, the reduced diameter rearward end 164 of which is secured in a hole 166 in the center of the crosshead'160 midway between the two bearing bores 158 for the two inner tubular shafts 154.

The rack shaft 162 passes slidably through the bearing bore 135 in the bearing bushing 134 (Figure 13) and at its opposite end is slidably mounted in a suitably bored bearing boss 168 in the end wall 54 from which it projects a sufficient distance to permit adequate reciproca ion while receiving bearing support from the bearing bushing 134 and bearing boss 168. The rack shaft 162 on its underside is provided with rack teeth 170 which mesh with a toothed quadrant 172 (Figure 2) on the upper arm 174 of a quadrant lever 176. The quadrant lever 176 is forked below its upper arm 174 (Figure 21) with laterally-spaced parallel lower arms 178. The lower arms 178 near their junction with the upper arm 174 carry a fulcrum block 180 between them, held in place by fulcrum pins 182 passing through the lower arms 173. The block 188 is bored. as at 184 to receive a slide shaft 186, one end of which is slidably mounted in a suitable-bored bearing boss 188 in the end wall 54 of the housing structure 42, and the other end of which is similarly mounted in the suitably bored upper end of an angle bracket 130 (Figure 2) which is bolted or otherwise secured to the inner .wall 50 of the housing structure 42.

The fulcrum block 180 and the slide shaft 186 on which it is mounted are reciprocated slowly to and fro to change anaemic the *pesiticn of the fulcrum or the lever 176 by a forked upperlink '192, theparallel arms 1% of which pivotally engage thefulcruzn pins 182. The opposite end 196 of the forked link 192 carries a loop 198 which forms the outer element of a variable stroke adjustment device, generally designated 280, described in more detail below. Mounted between the lower ends of the lower arms 1 78 of thequadrantlever 176 and secured thereto by a pivot pin "2tl2'is-the forwardend 204 of a lower link 206, the rearward end of whichterminates in a loop 208 forming the outer element of a variable stroke adjustment device, generally designated 210. The variable stroke adjustment devices 206 and-210 are of similar construction, hence thesingle description of the device 2 will sufiice for both.

The variable stroke adjustment device 200 or 210 (Figures l0 and l1) is, as its name suggests, for the purpose of enabling-thestroke of the upper link 192 or the lower link 266 to bevaried in order to vary the stroke and range of reciprocation of the rack shaft 162. The'loo'p 198 or 208 in which the upper link .192 orlower link 206 terminates is provided with a bore 212 concentric therewith and receiving an eccentric ring 214 having an outer cylindrical surface 216 rotatably engaging the bore 212 and having a center located at the point 218. Theeccentric ring 214- has a cylindrical bore 220 therein with a center 222 displaced from the center 218 'of its outer surface 216, and also has a small bore 224 near the periphery thereof for the reception of a rotary setting tool or key 226 in the form of a' pinion rod (Figure 12') havingv a'smooth rod portion 228 at one end of which is ahan-dle (not-shown) and at the other end pinion teeth 230 which are fiu'shwith the smooth surface of the smooth portion 228. The setting tool 226 is'slightly smaller in: diameter than the small bore 224 was to be insertable therein,'with its pinion teeth 230 projecting-through the other end into meshwith gear teeth 232 on the periphery ofage'ar 234 (Figure 3),-the hub 2360f which is cylindrical andfits into "the inner eccentric bore 226 in the eccentric ring 214. Beyond its teeth 232 (Figures 3 and 10), the gear 234 has-'a-retaining flange 238 and at its opposite end is engaged by a disc 240c'ontaining a pin 242 projecting into asocket 244in the gear'hub 236. The gear hub 236 is provided with'an eccentric bore 246 within which is keyed,-as M248, the-reduced diam'eterend portion 2500f a shaft 252, the end portion 250 passing through the disc 240 and the assembly being held in position by a nut 254 threaded upon the end thereof. The eccentric ring-214is-fianged and held in place against the loop or annular portion 2 38 of the'link 206 by a stepped retaining ring 256 secured thereto by the screws 258.

The shaft 252 is journaledin a bore 260 in a bearing boss-262 inthe housing wall (Figure 3') and keyed as at 264 to its inner endare a spur gear 266 and a bevel pinion 268 arranged in tandem. The spur gear 266 meshes with and is driven by the-clutch output gear 116 of-the multiple disc clutch 68. Meshing with the'bevel pinion268 is a bevel pinion 270 pinned to the lower end of an upwardly inclined shaft 272 journaled in a bearing bracket 274 (Figures 1 and 2) and having a worm 276 pinned to its upper end. The worm 276 meshes with a worm gear or worm wheel 278 which is keyed or otherwise secured to the inner end of a shaft 280. The shaft 28tl'is j'ournaled in a bore 282 in a bearing boss 284 carried by the inner housing Wall 50, and the outer reduced diameter end'portion 286 is keyed to the gear hub 234 of the upper variablestroke adjusting device 200 in the same manner as the reduced diameter end portion 250 of the lower shaft 252. Due to the speed reduction brought about by the worm 276 and worm gear 278, however, the upper shaft 280 rotates at a much slower rate than thelower shaft 252, with the result that the upper link 194 and the'fulcr'um block 130 andslide rod 186 reciprocate much more slowly than 'the lower link 206 and the quadrantlever 1-76 to which it is connected.

The for-ward end 'ofea'ch inner tubiilarshaft 154 enters and terminates within a bore '290 (Figure 6) "within the outer -'sleeve 292 of a workpiece "holder, generall desig- Dated 294, and is drivingl'y connected thereto by a s'et s'crew 296 threadedinto the 'one and-penetrating the other. The outer sleeve 29 2 is provided with inner and ohter counterb'ores 298 and 300 respectively (Figfu'reG) cemrn'unicating' with and coaxial with'thebore-29 0. Moufnted in the outer counterbore 300 is the self-'aligning'finner sleeve 302 having anannular spherical portion 304 611- gaging the outer counterbore 300 a'nd an internallytlang'ed inner cylindrical portion 3060f smaller diameter projecting into the inner counterbore 298 with a-sufficieht clearance therebe'tween to permit a slight self-aligning o'r rockingmotion'of theinn'er sleeve302'within the outer sleeve 292. Mounted at opposite ends of thes'phe'ricar portion304 of the'inner'sleeve 302'are resilient oryielding rings 308 and 310 of compressible material, the latter being engaged by a retaining ring 312 which is se cured to the outer sleeve 292 by 'thescrews 314.

The inner'sleeve 302 is provided with a central bore 316 which is threaded at its outer end to "receive a threaded tlangecbcollar 318 bywhich the work'piece'320 to be lapped is held in position 'within the bore 316 and against the annular shoulder 322 at the inner e'nd there'of (Figure 6). The workpiece 320 is shown, for put-poses of example, as a bushing with a bore 324 to be lap ed. The bore 324 passesthrough both thelarge diameter and small diameter-portions 326 and 328'respectively of 'the workpiece 320', the retaining collar 31 8-fitting arouhdthe' reduced diameter portion 328. The'workpie'c'e 320 is driven by rotation transmitted to it-fromthe outer sleeve 292 by the frictional engagement of the rin'gs 308-and 310 with the opposite ends of the spheric'al portion 304' of the inner sleeve 30 2.

Automatically-expansible lapping -meizanism The automatically-expansible lapping mechanism, generallydesignated 330 (Figures 1, 2, 4, 6m 8 inclusive,

l4 and 15') has anexpansible'lap which extends-into the workpiece bore 324 (-Fig'ure 6),-and=is automatically expanded as the lapping progresses,in order to conform=to the increasingsize of the bore 324. In thismechanism 336, the expansible lap-itself does not reciprocate, butremains stationary by beingheld against an adjustable abutment which accurately locates tlrelap Within the bore while the workpiece 320 is simultaneously "rotated and reciprocated by the mechanismfjust described-above. This lap abutment, generally designated 332, consists of ared having an enlarged portion 334 (Figure 6) accurately-fit-- ting and-slidable within'the bore 155 of theinnentubular shaft 154. The enlarged-portion334=has areduced diam eter tubular forwardportion 336'with anabutment-end 338 at the forward end of a cylindricalbore orsdcket 340into which a portionof the-lapprojects as'described below. Extending rearwardly-from the enlargement 334' is an elongated smaller diameterportion342, the rearward endtportion of which is threaded asat- 344,- and terminates in a knob or handwheel 346 Figure2). The threaded portion 344 is threaded through an internally-threaded flange bushing 348 Which is-jseatedin a-hole' 350-in -thehousing end wall 52 and held in position by a lookout 352. An internally-threaded hand wheel 354threaded upon the-outer portion of thethreaded part 344 serves as a lock nut for holding the lap abutment 332-in-itsadjusted position. By rotating the hand wheel 346 after completing the lapping of a workpiece, the position of the abutment end 338 (Figure 6) is varied so as to-reduce' the diameter of the lapping tool before startingto lapthe next workpiece.

The expansiblelap generally designated 356 (Figure 6) consists of 'a tubular. external lappingz membe'r 358 having an elongated slot 360 extending through the side wall thereof from end to end (Figures 14 and 15) and a tapered or conical bore 362 therethrough with a circular distribution of transverse or radial ports 364 extending from the tapered bore 362 to the outer cylindrical lapping surface 366 which engages and laps the workpiece bore 324. The slot 360 and the ports 364 conduct lapping compound'to the bore 324 to be lapped (Figure 15), so as to distribute the lapping compound evenly over the surface of the bore 324. The rearward end 368 of the external 362 and 3740f the tubular external lapping member 358 is an elongated expander, generally designated 376, of hardened highly polished material, such as steel. One

end portion 378 of the expander 376 is tapered or conical to conform to the conical bore 362 and at its extreme forward end is slidably-received for guidance within the end bore or socket 340 in the lap abutment 332 (Figures 6, 14 and 15. The opposite end portion 380 of the expander 376 is straight and conforms to the straight bore 374, which it slidably engages' It also passes through and slidably engages the bore 382 in the spacer 372 and is received within the bore 384 in the tubular gripping member 386 of a chuck 388. The lap expander 376 is provided with an elongated central passageway 390 for supplying lapping compound, and this communicates with radial ports 392 leading to the ports 364. The ports 364 are preferably slightly larger in diameter than the ports 392 in order to maintain communication without obstruction as the expander 376 is moved to and fro within the tubular lapping member 358.

The gripping member 386 has a longitudinal slot 394 and an externally conical surface 396 which engages the internally conical surface 398 of an outer stationary chuck member 400 (Figure 6) so that longitudinal shifting of the gripping member 386 relatively to the stationary tubular chuck member 400 causes the gripping member 386 to expand or contract so as to release or more tightly grip the end of the lap expander 376 respectively. One end of the stationary tubular outer chuck member 400 and one end of the gripping member 386 are covered by an internally-threaded cup-shaped cap 402 against which one end of the -tubular spacer 372 abuts. The cap 402 is provided with a central hole 404 for the passage of the lap expander 376. 'The rim of the cap 402 abuts the front face of an upright 406 at the forward end of a carriage 408 which has a base 410 (Figures 2 and 5) grooved as as 409 and 411 to slide to and fro along spaced parallel ways 412 on the upper side of each housing extension 46. The upright 406 is provided with a bore 414 which receives a stationary bushing 416 in the bore 418 of which the chuck 388 is bodily movable to and fro (Figure 6). The stationary bushing 416 is externally threaded at one end to receive the internally-threaded cap 402 and has an externally-threaded enlargement 420 which serves not only as an abutment for securing it in the bore 414 of the upright 406 by means of the cap 402, but also serves to receive an internally-threaded ratchet wheel or drum 422 by means of which the chuck 388 and the lap expander 376 are moved bodily to and fro.

The major portion of the stationary tubular chuck member 400 has a straight bore 424- (Figure 6) which terminates in the conical or flared portion 398 previously mentioned, and the inner end of the gripping member 386 is similarly straight so as to slide within the bore 424. The gripping member 386 of the chuck 388 is secured by its threaded end portion 426 to the internally-threaded socket 428 of an elongated tubular member 430, the outer end of which is threaded to receive a nut 432 which engages :the outer end of the tubular chuck member 400 so as to 498 in the upright 406 (Figure 2).

enable the internal or gripping member 386 to be moved into the external tubular member 400 in order to clamp the lap expander 376 within the bore 384. The tubular member 430 terminates in a reduced diameter threaded portion 434 which receives the coupling 436 of a flexible metallic hose 438 for supplying lapping compound to the bore 440 of the tubular member 430 and thence to the passageway 390 of the expander 376 of the lap 356.

The ratchet wheel 422 is in the form of a collar having a bore 442 which loosely and rotatably receives the reduced diameter portion 444 of the outer tubular chuck member 400, and is held thereon by an internallythreaded retaining ring 446 threaded onto the outer end portion of the outer tubular chuck member 430. The ratchet wheel 422 is also annularly grooved as at 448 to loosely and rotatably receive the annular pawl-inactivating member 450 (Figure 8) having a pawl rest 452 which projects axially over the elongated ratchet teeth 454 of the ratchet wheel or drum 422. The base ring 450 has an index mark 456 which registers with graduations 458 on a hand wheel 460. The hand wheel 460 is secured by the screws 462 to the outer end of the ratchet wheel 422, thereby also acting as a retainer for the pawlinactivating member 450. The outer end of the annular pawl-inactivating member 450 is provided with multiple circumferentially-spaced recesses 464 with rounded bottoms (Figure 7) engageable by the correspondinglyrounded end of a detent plunger 466 mounted within a bore 468 in the hand wheel 460 and yieldingly urged into the recesses 464 by a spring 470 resting against a plug 472 closing the outer end of the bore 468. As a consequence, the pawl rest 452 of the pawl-inactivating member 450 may be moved manually to any desired location around the periphery of the ratchet wheel 422 so as to determine the number of teeth by which the ratchet wheel 422 will be advanced by the reciprocating pawl 474 before it runs up on the pawl rest 452 and thenceforth ceases to advance the ratchet wheel 422, as explained in connection with the operation of the invention.

The two pawls 474, of which there is one for each ratchet wheel 422 corresponding to each work holder 294 and expansible lap 356 (Figure 4) are mounted side by side (Figure 9) with their annular hubs 476 resting upon and engaging an eccentric head 478 on the end of a shaft 480 journaled in a bore 481 in the upright 406 and having a spur gear 482 pinned or otherwise secured to its opposite end. The pawl hubs 476 are retained in position on the eccentric head 478 by a retaining disc 484 bolted as at 486 to the end of the shaft 480. Tension springs 488 anchored at one end to the upright 406 (Figure 4) and at the other end to the pawl hub 476 urge the pawls 474 into yielding engagement with their respective ratchet teeth 454.

Meshing with the gear 482 on the shaft 480 is an idler pinion 490 (Figure 9) mounted on a headed stud 492 secured in the bore 493 in the upright 406, the idler pinion 490 in turn meshing with a gear 494 pinned or otherwise secured to a shaft 496 journaled in the bore The opposite end of the shaft 496 is provided with an elongated spline. keyway or the like 500 by which it may move longitudinally in accordance with the motion of the carriage 408 along the guideways 412. The gear hub 502 of a gear 504 has a bore 506 through which the shaft 496 passes, and contains means, such as a keyway and key (not shown), for maintaining a driving connection with the spline or keyway 500 while permitting the shaft 496 to move longitudinally. As a consequence, rotation of the outer tubular shafts 146 is transmitted to the pawl eccentric shaft 480, the eccentric 478 of which causes the pawl 474 to reciprocate alternately each revolution of the shaft 480, thereby rotating the ratchet wheels 422 one tooth for each revolution of the shaft 480 until the.

pawls 474 ride- 11p on 1 their "respective "pawl re'sts" 452, halting further longitudinal motion of the'lap' expander 476 and thus halting further expansion of the tubular lapping member 358.

Automatic lapping compound feeding unit In order to supply lapping compound in the form of a paste evenly to the expansi'ble lap 356, an automatic lapping compound feeding unit, generally designated 510, is mounted on the base 410 of the carriage 408 (Figures 1, 2 and 5) and is driven by a bevel pinion 512keyed or otherwise secured to the outer end of the shaft 496. The bevel pinion 512 meshes with a bevel gear 514 pinned or otherwise drivingly secured to a headed vertical shaft 516 which is rotatably mounted in a vertical bore 518 in the carriage bed 410 (Figure 2). The upper periphery of the bevel gear 514 is provided with a boss 520 which carries a pivot pin 522 on which is mounted a bellcrank pawl 524 (Figure 5). One arm of the pawl 524 is connected to a tension spring 526 anchored to the carriage bed 410, thereby resiliently urging the other arm of the pawl 524 into yielding engagement with a ratchet wheel 528 having a hub 530 which is loosely and rotatably mounted in a 'bore 532 in the lower end of a lapping compound feeding cylinder 534 (Figure 5) and retained therein by a retaining nut 536 threaded on the upper end of the hub 530. The hub 530 is provided with a threaded bore 538 which threadedly engages an externally-threaded piston rod 540 carrying a piston head 542. The piston head 542 is reciprocably mounted in the cylinder bore 544 of the cylinder 534 and grooved to receive a piston ring 546 to prevent leakage of lapping compound past the piston head 542. The piston rod 540 is received within a vertical hole or socket 548 in the carriage base 410.

The cylinder 534 near its upper end is provided with opposite ports 550 (Figure 5) in externally-threaded bosses 552 to which are connected hose couplings 554 on the outer ends of the flexible metallic hoses 438. The upper end of the cylinder 534 is open and externallythreaded to receive a cover 556 by which the cylinder bore 554 may be refilled with lapping compound. The carriage base 410 is provided with a vertical bore 558 in which a vertical screw shaft 560 is rotatably mounted. Secured to the upper end of 'the's-crew shaft 560 is a handle in the form of an arm 562 for rotating the screw shaft 560. The lower end of the screw shaft 560 is threaded through a vertical threaded hole 564 in a clamping member 566 which engages the bottom'surface 568 of its respective housing extension 46 and extends partway upward into a slot 570 on the upper side thereof. Consequently, swinging of the handle 562 in one direction pulls the clamping member 566 upward against the housing extension 46 to lock the carriage 408 in position, while swinging the handle 562 in the opposite direction moves the clamping member 566 downward to release the carriage 408 so that it may be slid along its guideways 412.

External lapping attachment The lapping machine 30 is shown in Figures 1 to 16 inclusive as set up for internally lapping a workpiece 320, namely by lapping its bore 324 with the expansible lap 356. Figures 17 to 20 show details of the external lapping att-achment 40 for externally lapping a workpiece 572 while it is held in a chuck 574 shaped similarly-to the workpiece 320 so as to replace the latter in the bore 316 (Figures 6 and 17), in the inner sleeve 302 of the workpiece holder 294. The chuck 574 is thus'provided with an enlargement 576 and a reduced diameter portion 578 engaged by the threaded flanged collar 318 in the same manner as the workpiece'320 of Figure 6. The chuck 574 has a tapered nose or jaw portion 580 which is split longitudinally as 216582 to provide jaws with a bore 584 for receiving the workpiece 572 and 10 with an elongated counterbore 586for receiving the remainder of the workpiece 5 72 beyond the nose'or jaw portion 580 of the chuck 574. The nose or jaw portion 580 is externally threaded to receive an internallythreaded collar or out 588 'by which the jaw portion 580 is caused to grip or to release the workpiece 572.

The external lapping attachment 40 consists of a carriage 590 (Figure 17) having a base or bed 592 grooved similarly to the bed 410 of the carriage 408 in order to be interchangeable with the carriage 408 on the guideways 4-12. The carriage 590 is also provided with a clamping handle 594, clamping screw 596 and clamping member 598 corresponding to the clamping handle 562, clamping screw 560 and clamping member 566 of the carriage 408 and for the same' purpose. The carriage 590 is provided with an upright structure 600 which is provided with a pair of laterally-spaced bores 602 (Figure '18). Mounted in each of the bores 602 is a lap holder shaft 604, each of which is keyed as at 606 (Figure 18) to'the upright structure 600 toprevent rotation thereof in its respective bore 602. The lap holder shaft 604 is provided at its forward end with a reduced diameter portion 608 on which is mounted a collar 610 pinned thereto and carrying circumferentially-spaced pairs of cars 612. Each pair of cars 612 is drilled to receive a pivot pin 614 on which is mounted a lap holder lever 616, the forward end of which is provided with a threaded hole 618 (Figure 19) containing a flanged threaded bushing 620 held in place by a lock nut 622 and having an internally-threaded bore 624- which receives an externally-threaded lapping pin or rod 626 with a lapping tip 628 on the inner end thereof. By this construction, the lapping rods 626 are arranged radially to the workpiece 572 at circumferential intervals therearound.

The rearward end 630 of each lever 616 is rounded (Figure 17) and engages an internal conical surface 632 on a lever-actuating member 634 in the form of a hollow conical shell attached to a grooved annular shift member 636, the groove 638 of which is engaged by pins or rollers 640 and 642 (Figure 18). The outer pins or rollers 640 are mounted in the outer ends of an arcuate shift yoke 644 which has a central lever 646 rising therefrom and carrying bosses 648 which in turn carry the inner shift pins or rollers 642 diametrically opposite the outer shift rollers 640. The shift lever 646 (Figure 18) is drilled as at 650 to receive a pivot bolt 652 which passes through the similarly-drilled parallel ears 654 of a pivot bracket 656, the base 658 of which is bolted as at 660 to the top of the upright structure 600. Pivoted as at 662 to the shift lever 648 is a locking lever 664, the upper end of which is U-shaped in cross-section to pass on opposite sides of the upper end of the lever 648, a compression spring 666 being mounted in a socket 668 to urge the upper end 670 of the lever 664 outward away from the upper end 672 of the lever 648. The lower end portion 674 of the locking lever 664 is bent at an angle to the upper portion 670 thereof and carries a locking tooth 676 engageable with notches 678 in the ears 654. As a consequence, by shifting the handle 672 to and fro, the conical shifting member 634 is also shifted to and fro, swinging or permitting swinging respectively of the lap-holding levers 616 toward or away from their'sup'porting shaft 604 and consequently moving the lap tips 628 toward or away from the workpiece 572.

Each of the lap-holding levers 616 (Figure 17) is provided with a recess 680 forming a socket for the outer end of a spring 682, the inner'end of which is mounted in a socket 684 in the shaft 604. Thecenter of the shaft 604 is provided with an axial bore 686 which serves to receive the free end of the workpiece 572 during the lapping operation. The outer end 688 of the shaft 604 is threaded to receive a retaining nut 690 and washer 692.

The pivot pins 614 on which the lap-holding levers 616 are pivoted (Figure ZO) are'mount'ed in aligned h'oles 11 694 in the parallel ears 612 and each pivot pin 614 passes through an aligned bore 696 in the lever 616. Each pivot pin 614 is drilled and threaded as at 698 to receive a retaining screw 700.

The lapping compound may consist of various abrasives in a suitable paste, such as, for example, silicon carbide or corundum (aluminum oxide) preferably artificially produced to insure uniform properties, and mixed with a suitable grease, such as a petroleum grease, in order to give a paste-like consistency. This lapping compound is suitable for lapping workpieces of cast iron, steel and other metals as well as glass, porcelain and synthetic materials. The conical expander 376, as previosuly stated, is preferably made of hardened highly polished steel, Whereas the lapping shell 358 is preferably made of a high quality cast iron. The amount of expansion required during a lapping operation is of course very small, so that the cast iron shell is sufficiently resilient to expand the necessary amount without fracturing. A high quality cast iron with uniform resilience throughout is advisable for high precision work, in order to give uniform expansion of the lapping shell 358.

Operation of the machine for internally lapping workpieces In the operation of the invention, let it be assumed that the bore of a hollow tubular workpiece is to be lapped to a certain diameter and that an expansible lap 356 has been prepared with the lapping shell 358 of suitable diameter and of sufiicient length so that at least two-thirds of the lapping shell 358 will always be within the bore 324 of the workpiece 320 during the reciprocation thereof. A test workpiece 320 is mounted in the self-aligning inner sleeve 302 (Figure 6), which has been prepared with a suitable diameter of bore 316. The carriage 408 is retracted along the guideways 412 until sufficient space exists between it and the workpiece holder 294 for insertion of the workpiece 320 therein as well as for insertion of the expansible lap 356 in the chuck 388. The lock nut or looking hand wheel 354 (Figure 2) is loosened so that the hand wheel 346 can be rotated to advance or retract the lap abutment rod 332 within the inner tubular shaft 154 until its forward or abutment end 338 is properly positioned to locate the lapping shell 358 at the correct location within the test workpiece 320. The lock nut or locking hand wheel 354 is then tightened against the threaded bushing 348 to lock the abutment rod 332 in its adjusted position.

The expansible lap 356 is then assembled by sliding the lapping shell 358 onto the conical expander 376 (Figure 6.), the latter being coated with lubricating oil to prevent jamming or sticking together of the parts and permit their later separation from one another. A tubular spacer 372 of suitable length is then slid over the exposed small diameter end of the expander 376, the nut 432 is loosened on the end of the tubular member 430 to open the tubular gripping member 386 of the chuck 388, whereupon the small diameter end 380 of the expander 376 is inserted in the bore 384 of the gripping member 386 until the end of the tubular spacer 372 engages the cap 402. The nut 432 is then tightened to cause the gripping member 386 to tightly grip the expander 376.

Assuming that the test workpiece 320 has been clamped in position within the inner sleeve 302 by the threaded collar 318, the carriage 408 is then moved forward so that the lapping shell 358 enters the workpiece bore 324, with the shell 358 unexpanded. The strokes of the upper and lower links 194 and 206 are then adjusted so that the workpiece holder 294 causes the workpiece 320 to reciprocate back and forth along the lapping shell 358 and at the same time always keep at least two-thirds of the length of the lapping shell 358 within the workpiece bore 324. This adjustment of stroke is made by adjusting the upper and lower stroke-adjusting devices 200 12 and 210, as explained in connection with the description thereof above.

With the lapping shell 358 brought into abutting engagement with the abutment end 338 of the abutment rod 332 by moving the carriage 408 forward a suflicient distance, the carriage clamping handle 562 is then swung so as to rotate the screw shaft 560 and bring the clamping member 566 into clamping engagement with the housing extension 55 (Figure 5). A supply of lapping compound of paste-like consistency is then placed in the cylinder 534 by removing the screw cap 556 thereof, the piston 542 having been retracted to its lowest position by lifting the pawl 524 away from the ratchet wheel 528 with one hand while rotating the ratchet wheel 528 with the other hand in order to retract the threaded piston rod 548. The rotation of the ratchet wheel 528 is then reversed to force lapping compound through the hoses 438 and bores 440, 384 and 390 (Figure 6) and transverse ports 392 and 364 (Figures 14 and 15) into the workpiece bore 324. The pawl 524 is then permitted to re-engage the ratchet wheel 528.

The machine is then started in operation and an experimental lapping operation is then performed on the test workpiece 320 by causing it to be simultaneously rotated and reciprocated by means of the mechanism shown in Figure 2. The irregular motion imparted to the workpiece holdcr 294 by the swinging of the quadrant lever 176 by the lower link 206 while its fulcrum 182 is also being irregularly reciprocated by the upper link 194 causes the reciprocation to be entirely irregular, without ever recurring in the same phase, or at least not until after a long period of operation. This irregularity of reciprocation, coupled with the rotation of the workpiece 320, insures accuracy of lapping by preventing deformitics thereof due to repeated movement of the lap over the same portions of the workpiece in the same phase, as has occurred in prior lapping machines.

Meanwhile, the machine operator, after noting the starting reading of the scale 458 (Figure 8) at the index mark 456, manually expands the lapping shell 358 by gradually rotating the hand Wheel 460, inspecting the workpiece from time to time to observe the progress of lapping. Meanwhile, the lapping compound has been fed automatically to the workpiece bore 342 in the manner previously described, the reciprocation of the workpiece and its simultaneous rotation distributing the lapping compound in an even layer or film throughout the workpiece bore 324. When the inspection shows that the bore 324 of the test workpiece 320 has been fully lapped to the correct dimensions, the operator stops the machine and again notes the reading of the scale 458. The difference between the final reading and the starting reading of the scale 458 gives the amount of rotatation of the ratchet wheel 422 which is henceforth necessary in order to perform the lapping properly and sufiiciently.

The operator then unclamps the carriage 408 by means of the clamping handle 562, retracts the carriage 408 and the expansible lap 356 until they are withdrawn from the workpiece bore 324 (Figure 6), unscrews the retaining collar 318, removes the test workpiece 320, and replaces it with the first of the series of workpieces to be commercially lapped. He then inserts the expansible lap 356 in the bore 324 of the new workpiece 320, having first contracted the shell 358 upon the expander 376 in order to reduce its diameter to the minimum. The operator then sets the pawl rest 452 of the pawl inactivating member 450 (Figures 7 and 8) at a sufficient distance from the tip of each pawl 474 so that the pawl 474 will turn the ratchet wheel 422 step by step the same rotational distance indicated by the manual operation of the hand wheel 460 in lapping the test workpiece, as just explained above.

The operator then restarts the machine and repeats the foregoing operations. The new workpiece 320 is rotated and reciprocated irregularly while the reciprocation of the pawl 524 rotates the horizontal ratchet wheel 528 step by step to move the threaded piston rod 540 and piston head 542 upward in the lapping compound feeding cylinder 534, automatically feeding the lapping compound to the expansible lap 356 in the manner previously explained. At the same time, the simultaneous reciprocation of the pawls 474 by the rotation of the eccentric shaft 478 (Figure 4) rotates the ratchet wheels 422 step by step until the pawl rests 452 are carried around into engagement with the pawls 474. The pawls 474 then ride up on the pawl rests 452, halting the further expansion of the lapping shell 358 by halting the pulling of the lap expander 376 to the right (Figure 6) while the lapping shell 358 itself is held stationary between the end 338 of the abutment rod 332 and the tubular spacer 372 which is then in engagement with the cap 402 abutting the carriage upright .406. During the lapping operation, of course, the carriage 4&8 is clamped to its guideways 412 by swinging the clamping handle 562 as previously explained.

When the lapping is completed, after the lap-expanding pawls 474 have ridden up on the lap rests 452, the operator shifts the particular clutch handle 114 which disengages the clutch 68 (Figure 3) controlling the rotation and reciprocation of the particular pair of workpiece holders 294 in which the lapping has just been completed. He then shifts the carriage 408 to its retracted position in the manner explained above, in order tounload the lapped workpieces 320 from the work holders 294 andinsert an unlapped pair of workpieces. The operation of themachine can thus be arranged so that the workman is loading or unloading one pair of work holders 294 while-the other pair is engaged in lapping a pair of workpieces, with the result that at least one pair of the four spindles of the machine is always rotating and reciprocating, even though the other pair is temporarily idle forloading or unloading purposes. The automatic expansion of the lap 356 gives a controlled lapping rate, time and dimension and the automatic feed of lapping compound insures that only the correct amount of lapping compound is fed, at the most suitable rate of speed, to the workpiece bore being lapped, and also that fresh lapping compound is constantly supplied to the workpiece bore being lapped. The result is a lapping procedure of greatly increased accuracy over that previously obtainable with prior lapping machines, together with absolutely straight bores of constant diameter, free from flared or bell-mouthed ends and also free from irregularities or non-circular portions.

Operation of machine for externally-lapping workpieces To externally lap a workpiece, such as the rod 572 in Figures 17 to 20 inclusive, the internal lapping carriage 408 is unclamped and removed from the guideways 412, together with the expansible lap 356, and replaced by the external lapping unit 40 (Figure 17). The chuck 574is mounted in the inner sleeve 302 of the workpiece holder 294 in place of the workpiece 320, and secured in position by the threaded collar 318. With the nut v588 loosened upon the threaded nose portion 580 of the chuck 574, the workpiece 572 is inserted in the chuck bore 584 and the nut 588 tightened to clamp the workpiece572 in the chuck 574.

The lapping pins 626 are then adjusted radially in their respective bushings 620 (Figure 19;) until all are properly positioned so that their tips 628 come into simultaneous contact with the surface of the workpiece 572. The lock nuts 622 are then tightened to lock the lapping pins 626 in their adjusted positions.

The operator then manually applies lapping compound to the workpiece 572, slides the carriage forward until the lapping pins 626 arrive at the end of the workpiece 572, arid starts the machine in operation as described above. By swinging the handle 648 to the right so as tomove :the. conical member634, the tips 628 of the lapping pins626 can' be moved out of contact with the workpiece -572, otherwise they areresiliently urged by the springs 682 into :contact with the workpiece 572 while it :is being simultaneously rotated and reciprocated. The carriage 590 is moved, as desired, to lap a different portion of the workpiece 572 which has not been reached by its simultaneous reciprocation and rotation, and the workpiece itself can be replaced end for end in the chuck 574 to lap the unlapped end previously held in the chuck. In this manner, by the substitution of the external lapping unit 40 forthe internal lapping mechanism as described above, workpieces can be lapped either externally or internally in otherwise the same machine, and precision of external lapping also greatly enhanced.

What I claim is:

l. A precision lapping machine comprising a workpiece holder configured to grip the workpiece to be lapped, a lapping tool engageable with said workpiece and having an external expansible lapping element and internally thereof a lap-expanding element, a lapping tool holder adapted to receive said lapping tool, mechanism for rotating one of said holders relatively to the other holder, mechanism for reciprocating one of said holders relatively to the other holder, and means operable in timed relationship with one of said mechanisms for automaticallymoving said lapping tool elements relatively to one another to expand said lapping tool during lapping engagement thereof with said workpiece; said lapping tool element-moving means including a stationary structure having an abutment engageable with one of said elements, an axially movable :member connected to the other element, a first threaded member connected to said stationary structure, a second threaded member threadedly engaging said first threaded member and connected to said axiallymovable member, a ratchet wheel connected to said second threaded member in driving relationship therewith, a reciprocatory pawlengageable with said ratchet wheel, a pawl lifter rotatably mounted coaxial with said ratchet'wheel and having a pawl-lifting portion selectively movable into and out of the path of said pawl, said pawl lifter being operatively connected to said ratchet wheel for. rotation therewith into inactivating engagement with said pawl, and means connected to one of said mechanisms for reciprocating said pawl to rotate said ratchet wheel.

2. A precision lapping machine comprising a workpiece holder configured to grip the workpiece to be lapped, a lapping tool engageable with said workpiece and having an external expansible lapping element and internally thereof a lap-expanding element, a lapping tool holder adapted to receive said lapping tool, mechanism for rotating one of said .holders relatively to the other holder, mechanism for reciprocating one of said holders relatively to the other holder, and means operable in timed relationship with'oneof said mechanisms for automatically moving said lapping tool elements relatively to one another to expand said lapping tool during lapping engagemcnt thereof with said workpiece; said lapping tool element-moving means including a stationary structure having an abutment. engageable'with one of said elements, an axially-movable member connected to the other element, a first threaded member connected to said stationary structure, a second threaded member threadedly engaging said first threaded member and connected to said axially-movable member, a ratchet wheel connected to said second threaded member in driving relationship therewith, a reciprocatory pawl engageable with said ratchet wheel, a pawl lifter disposed in the path of said pawl, said pawl lifter being operatively connected to said ratchet wheel and adjustably mounted thereon for rotation therewith into inactivating engagement with said pawl, and means connected to one of said mechanisms for reciprocating said pawl to rotate said ratchet wheel.

3. A precision lapping machine comprising a workpiece holder configured to grip the workpiece to be lapped, a lapping tool engageable with said workpiece and having an external expansible lapping element and internally thereof a lap-expanding element, a lapping tool holder adapted to receive said lapping tool, mechanism for rotating one of said holders relatively to the other holder, mechanism for reciprocating one of said holders relatively to the other holder, and means operable in timed relationship with one of said mechanisms for automatically moving said lapping tool elements relatively to one another to expand said lapping tool during lapping engagement thereof with said workpiece; said lapping tool elementmoving means including a stationary structure having an abutment engageable with one of said elements, an axiallymovable member connected to the other element, a first threaded member connected to said stationary structure, a second threaded member threadedly engaging said first threaded member and connected to said axially-movable member, a ratchet wheel connected to said second threaded member in driving relationship therewith, a reciprocatory pawl engageable with said ratchet wheel, a pawl lifter disposed in the path of said pawl, said pawl lifter being operatively connected to said ratchet wheel and adjustably mounted thereon for rotation therewith into inactivating engagement with said pawl, a latch releasably locking said pawl lifter to said ratchet wheel, and means connected to one of said mechanisms for reciprocating said pawl to rotate said ratchet wheel.

a 4. A precision lapping machine comprising a workpiece holder configured to grip the workpiece to be lapped, a lapping tool engageable with said workpiece and having an external expansible lapping element and internally thereof a lap-expanding element, a lapping tool holder configured to grip said lapping tool, mechanism for rotating one of said holders relatively to the other holder, mechanism for reciprocating one of said holders relatively to the other holder, said lapping tool having a lapping compound feeding passageway therethrough leading to the outside of said external lapping element, a lapping compound receptable having an outlet communieating with said passageway, and lapping compound feeding means connected to said receptacle and operatively connected in timed relationship with one of said mechanisms for automatically feeding the lapping compound to said passageway.

5. A precision lapping machine comprising a workpiece holder configured to grip the workpiece to be lapped, a lapping tool engageable with said workpiece and having an external expansible lapping element and internally thereof a lap-expanding element, a lapping tool holder configured to grip said lapping tool, mechanism for rotating one of said holders relatively to the other holder, mechanism for reciprocating one of said holders relatively to the other holder, said lapping tool having a lapping compound feeding passageway therethrough leading to the outside of said external lapping element, a lapping compound cylinder having an outlet communicating with said passageway, a piston reciprocably mounted in said cylinder and piston-reciprocating mechanism reciprocably engaging said piston and operatively connected to a moving part of said mechanisms for automatically feeding the lapping compound to said passageway in timed relationship with the motion of said moving part.

6. A precision lapping machine comprising a workpiece holder configured to grip the workpiece to be lapped, a lapping tool engageable with said workpiece and having an external expansible lapping element and internally thereof a lap-expanding element, a lapping tool holder configured to grip said lapping tool, mechanism for rotating one of said holders relatively to the other holder, mechanism for reciprocating one of said holders relatively to the other holder, said lappingtool having a lapping compound feeding passageway therethrough leading to the outside of said external lapping element, a

lapping compound cylinder having an outlet communicating with said passageway, and lapping compound feeding means including a piston reciprocably mounted in said cylinder, said piston having a threaded piston rod thereon, a rotary threaded member threadedly engaging said piston rod, and threaded member rotating means rotatingly engaging said threaded member and operatively connected to one of said mechanisms for automatically feeding the lapping compound to said passageway.

7. A precision lapping machine comprising a workpiece holder configured to grip the workpiece to be lapped, a lapping tool engageable with said workpiece and having an external expansible lapping element and internally thereof a lap-expanding element, a lapping tool holder configured to grip said lapping tool, mechanism for rotating one of said holders relatively to the other holder, mechanism for reciprocating one of said holders relatively to the other holder, said lapping tool having a lapping compound feeding passageway therethrough leading to the outside of said external lapping element, a lapping compound cylinder having an outlet communicating with said passageway, and lapping compound feeding means including a piston reciprocably mounted in said cylinder, said piston having a threaded piston rod thereon, a rotary threaded member threadedly engaging said piston rod, and threaded member rotating means rotatingly engaging said threaded member and operatively connected in timed relationship with one of said mechanisms for automatically feeding the lapping compound to said passageway.

. 8. A precision lapping machine comprising a workpiece holder configured to grip the workpiece to be lapped, a lapping tool engageable with said workpiece and having an external expansible lapping element and internally thereof a lap-expanding element, a lapping tool holder configured to grip said lapping tool, mechanism for rotating one of said holders relatively to the other holder, mechanism for reciprocating one of said holders relatively to the other holder, said lapping tool having a lapping compound feeding passageway therethrough leading to the outside of said external lapping element, a lapping compound cylinder having an outlet communicating with said passageway, and lapping compound feeding means including a piston reciprocably mounted in said cylinder, said piston having a threaded piston rod thereon, a rotary threaded member threadedly engaging said piston rod, and threaded member rotating means including a ratchet wheel rotatingly engaging said threaded member and a reciprocable pawl rotatingly engaging said ratchet wheel, and means attached to said pawl and operatively connected in timed relationship with one of said mechanisms for automatically feeding the lapping compound to said passageway.

References Cited in the file of this patent UNITED STATES PATENTS 516,543 Medart Mar. 13, 1894 1,878,656 Adams Sept. 20, 1932 2,164,867 Blood July 4, 1939 2,194,821 Crompton Mar. 26, 1940 2,287,559. Nye June 23, 1942 2,317,714 Ball Apr. 27, 1943 2,343,275 Caldwell Mar. 7, 1944 2,350,527 Peden June 6, 1944 2,669,073 Bendickson Feb. 16, 1954 FOREIGN PATENTS 403,948 Great Britain Ian. 2, 1934 490,236 France May 24, 1918 543,381 Great Britain Mar. 5, 1941 572,070 Great Britain Sept. 21, 1945 613,962 Great Britain Dec. 7, 1948 876,515 Germany May 15, 1953 897,057 Germany Nov. 16, 1953 France Apr. 23, 

